I lived in Egypt for a year and go there from time to time for business. It's a great city and the people are amazingly hospitable. You'll be fine, just don't look men in the eyes and dress a little more conservatively (the more scantily clad you are the more stares you will get).

I always enjoyed the Coptic Cairo section of town (lots of old Orthodox churches that all claim that Jesus slept there). Amazing place with great artwork. Great place to see that helps you remember that almost 10% of Egypt is Christian.

Of course, if you start missing home and need Western food, don't forget to stop by Chili's on the Nile (very close to the Marriott hotel in Zamalek)

Enjoy a great city!!!